This invention generally relates to a pattern display apparatus for motion pictures and more particularly relates to a method for marking a displayed motion picture image in order to discourage recording the image using a video camera.
Movie piracy is a cause of substantial revenue loss to the motion picture industry. Illegally copied movies, filmed during projection with video cameras or camcorders and similar devices, are a significant contributing factor to revenue loss. Even the questionable quality of movies pirated in this fashion does not prevent them from broad distribution in the xe2x80x9cblack marketxe2x80x9d, especially in some overseas markets, and on the Internet. As video cameras improve in imaging quality and become smaller and more capable, the threat of illegal copying activity becomes more menacing to motion picture providers. While it may not be possible to completely eliminate theft by copying, it can be advantageous to provide display delivery techniques that frustrate anyone who attempts to copy a motion picture using a portable video camera device.
It is known to provide a distinct symbol or watermark to an original still image as a means of image or copy identification, such as in order to authenticate a copy. As examples, U.S. Pat. No. 5,875,249 (Mintzer et al.), U.S. Pat. No. 6,031,914 (Tewfik et al.), and U.S. Pat. No. 5,912,972 (Barton) disclose methods of applying a perceptually invisible watermark to image data as verification of authorship or as evidence that an image has not been altered. However, where such methods identify and validate image data, they provide no direct means of protection against copying an image, such as using a conventional scanner and color printer. In contrast, U.S. Pat. No. 5,530,759 (Braudaway et al.) discloses providing a visible, color correct watermark that is generated by altering brightness characteristics but not chromaticity of specific pixels in the image. But the approach used in U.S. Pat. No. 5,530,759 could be objectionable if used for a motion picture, since the continuing display of a watermark on film could annoy an audience and adversely affect the viewing experience.
The above examples for single images illustrate a key problem: an invisible watermark identifies but does not adversely affect the quality of an illegal copy, while a visible watermark can be distracting and annoying. With video and motion picture images, there can be yet other problems with conventional image watermarking. For example, U.S. Pat. No. 5,960,081 (Vynne et al.) discloses applying a hidden watermark to MPEG data using motion vector data. But this method identifies and authenticates the original compressed data stream and would not provide identification for a motion picture that was copied using a camcorder. Other patents, such as U.S. Pat. No. 5,809,139 (Girod et al.), U.S. Pat. No. 6,069,914 (Cox), and U.S. Pat. No. 6,037,984 (Isnardi et al.) disclose adding an imperceptible watermark directly to the discrete cosine transform (DCT) coefficients of a MPEG-compressed video signal. These methods, however, provide a watermark that is primarily detectable in the compressed image data itself. If such watermarked images are subsequently recompressed using a lossy compression method (such as by a camcorder, for example) or are modified by some other image processing operation, the watermark may no longer be detectable.
The watermarking schemes disclosed in the patents listed above add a watermark to the compressed bit stream of an image or image sequence. Alternatively, there are other watermarking schemes that add the watermark to the image data itself, rather than to the compressed data representation. An example of such a scheme is given in U.S. Pat. No. 6,044,156 (Honsinger et al.), which discloses a spread spectrum technique using a random phase carrier. However, regardless of the specific method that is used to embed a watermark, there is always a concern that a watermarking method be robust, that is, able to withstand various xe2x80x9cattacksxe2x80x9d that can remove or alter the watermark. Some attacks may be deliberately aimed at the underlying structure of a given watermarking scheme and require detailed knowledge of watermarking techniques applied. However, most attack methods are less sophisticated, performing common modifications to the image such as using lossy compression, introducing lowpass filtering, or cropping the image, for example. Such modifications can be made when a video camera is used to capture a displayed motion picture. These methods present a constant threat that a watermark may be removed during the recording process.
The watermarking schemes noted above are directed to copy identification, ownership, or authentication. However, even if a watermarking approach is robust, provides copy control management, and succeeds in identifying the source of a motion picture, an invisible watermark may not be a sufficient deterrent for illegal copying.
As an alternative to watermarking, some copy deterrent schemes used in arts other than video or movie display operate by modifying a signal or inserting a different signal to degrade the quality of any illegal copies. The modified or inserted signal does not affect playback of a legally obtained manufactured copy, but adversely impacts the quality of an illegally produced copy. As an example of this principle, U.S. Pat. No. 4,644,422 (Bedini) discloses adding a degrading signal to discourage copying of audio recordings. An audio signal having a frequency at and above the high threshold frequency range for human hearing is selectively inserted into a recording. The inserted signal is not detectable to the listener. However, any unauthorized attempt to copy the recording onto tape obtains a degraded copy, since the inserted audio signal interacts adversely with the bias oscillator frequency of a tape recording head.
As a variation of the general method where a signal is inserted that does not impact viewability but degrades copy quality, U.S. Pat. No. 6,018,374 (Wrobleski) discloses the use of a second projector in video and motion picture presentation. This second projector is used to project an infrared (IR) message onto the display screen, where the infrared message can contain, for example, a date/time stamp, theater identifying text, or other information. The infrared message is not visible to the human eye. However, because a video camera has broader spectral sensitivity that includes the IR range, the message will be clearly visible in any video camera copy made from the display screen. The same technique can be used to distort a recorded image with an xe2x80x9coverlaidxe2x80x9d infrared image. While the method disclosed in U.S. Pat. No. 6,018,374 can be effective for frustrating casual camcorder recording, the method has some drawbacks. A more sophisticated video camera operator could minimize the effect of a projected infrared watermark using a filter designed to block infrared light. Video cameras are normally provided with some amount of IR filtering to compensate for silicon sensitivity to IR. With a focused watermark image, such as a text message projected using infrared light, retouching techniques could be applied to alter or remove a watermark, especially if the infrared signal can be located within frame coordinates and is consistent, frame to frame. A further drawback of the method disclosed in U.S. Pat. No. 6,018,374 relates to the infrared light source itself. Since an infrared lamp can generate significant amounts of heat, it may not be practical to project a watermark or copy deterrent image over a large area of the display screen using only an IR source.
Conventional methods such as those described above could be adapted to provide some measure of copy deterrence and watermarking for conventional as well as digital motion pictures. However, none of the methods noted above is wholly satisfactory, for the reasons stated. None of the existing copy protection or watermarking methods takes advantage of key characteristics of the digital motion picture environment. None of the above methods adequately provides a watermark or copy-deterrent marking that is not visually obtrusive during viewing, but at the same time can be recorded by a video camera.
The capability for encoding xe2x80x9cpassivexe2x80x9d invisible digital watermarks within video data has been developed. However, there is a need for more aggressive watermark and copy-deterrent protection that utilizes digital motion picture data content and that takes advantage of digital projector technology. In a fully digital motion picture system, frames are projected at precise intervals (usually at {fraction (1/24)} or {fraction (1/30)} second) and the spectral content of each displayed pixel is known for each frame. Each displayed pixel on the screen can be individually addressed within any frame, and its spectral characteristics can be identified. This capability has, however, not been used for watermarking or for displaying a copy-deterrent pattern.
In order to reduce the amount of data that needs to be stored for a recorded image, video cameras employ some type of image compression, such as JPEG or MPEG familiar in the image compression arts. Video compression schemes of this type take advantage of image predictability between consecutive frames in order to reduce the overall size of stored data. For film producers and distributors, however, it can be seen that there would be advantages to using display techniques that render JPEG, MPEG, and similar compression schemes ineffective for video camera users attempting to copy a motion picture from a screen. Methods for minimizing the effectiveness of compression schemes would be advantageous for copy protection of a motion picture, whether the motion picture is stored and displayed from conventional film reels or from a digital data source.
Therefore, it can be seen that there is clearly a need for a method that allows watermarking and copy-deterrent marking of motion picture content, where the content is generated from film or from digital data. It would be most advantageous for a marking to be invisible to a viewer but recordable using a video camera. Further, it can be seen that there is a need for a method that uses the opportunity for control of timing and of individual screen pixel content that digital motion picture technology offers in order to defeat movie piracy using a video camera.
With the above description in mind, it is an object of the present invention to provide a pattern display apparatus for displaying a pattern within a projected motion picture image frame, the apparatus comprising:
(a) an infrared light (IR) source adapted to provide infrared light to a first plurality of individual regions within said projected motion picture image frame;
(b) an ultraviolet (UV) light source adapted to provide ultraviolet light to a second plurality of individual regions within said projected motion picture image frame.
It is a feature of the present invention that it is capable of selectively illuminating one or more individual regions within both first and second plurality of individual regions based on spectral content of projected pixels within the motion picture image frame. This gives the present invention, for example, the capability to provide a watermark or copy-deterrent pattern that is very nearly visible in areas of a frame having a predominantly blue or red color content. An embedded pattern could also be an encoded digital watermark that identifies origin, ownership, or display attributes of a motion picture, where such a watermark can be securely encoded and decoded and used for identification purposes.
A further feature of the present invention is the capability to randomize region selections for ultraviolet or infrared sources with each frame. This feature contributes to the robustness of any watermark or copy-deterrent effect applied, since it makes it difficult to re-create image content affected by the watermark or copy-deterrent effect, except possibly on a frame-by-frame basis.
It is an advantage of the present invention that it provides an apparatus and method for marking or obscuring an illegally captured copy without affecting the image quality of a valid viewing for a motion picture.
It is a further advantage of the present invention that it provides a method for displaying a copy-deterrent effect or watermarking of a motion picture that is transparent to a viewing audience.
It is a further advantage of the present invention that it provides a method that makes it impractical to generate and use a copy of a motion picture filmed using a video camera. Significantly, the present invention provides a method and apparatus that can be effective for both digital motion picture and conventional, film-based motion picture projection.
These and other objects, features, and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention.